(a) Field of the Invention
The present invention provides an improved structure for a charger that uses a detector device to determine size of battery charge current, so that when the charge current has not yet reached a set value, then an automatic switching device switches the charger device to a boosting charge mode.
(b) Description of the Prior Art
A prior art charger connected to a battery has the function to cut off charging when the battery is fully charged. However, set values of prior art chargers are all set to voltage values of charge currents required by the normal internal resistance of batteries using the formula: V=I×R (Ohm's Law, where V=voltage, I=current, R=resistance). When the battery discharges to a voltage below one fifth of normal voltage, then it is referred to as an overdischarged battery, at which time, chemical transformation interior of the battery causes internal resistance of the battery to increase, and current is unable to flow into the battery, thereby prohibiting normal charging of the battery. Moreover, when voltage set values of the chargers are fixed to voltage values of the charge current required by normal internal resistance of batteries, then the charge current decreases when internal resistance of the batteries increases, even to the extent of no current flowing. Furthermore, when charge current decreases, many of the prior art chargers mistakenly assume the battery to be fully charged and cut off power, thus, the battery is unable to be charged or the battery is mistakenly assumed to be malfunctioning. Hence, if it is desired to resolve the problem of an overdischarged battery being unable to be charged, then the voltage set value must be increased to enable the current to produce a chemical transformation in the battery and restore a normal internal resistance, thereby achieving the objective of being able to charge the battery. However, the charge voltage cannot be set to be continuously at a high value, otherwise overcharging of the battery results. Hence, a control circuit must be used as additional control, so that when the charge current reaches a certain set value, then the charge voltage set value must restore a normal charge mode, thus, objective of charging the overdischarged battery can be achieved by increasing voltage set values of the charger.
Hence, the inventor of the present invention proposes to resolve and surmount existent technical difficulties to eliminate the aforementioned shortcomings of prior art.